Just three days after qualifying for the Europa League group phase, Christophe Galtier guided his side to a second win of the early domestic season thanks to a 20th minute strike from captain Loic Perrin and then a 62nd minute winner from on-loan Valentin Eysseric.
Bastia had pulled level four minutes before the break through Gael Danic but slip to sixth in the table after their first defeat in four outings.
In the second match on Sunday, Bordeaux picked up their first win of the season with a 2-0 victory over Nantes in a battle of former champions.
Tunisian midfielder Wahbi Khazri grabbed the all-important opener right on the stroke of half-time before 19-year-old Serbian defender Milan Gajic wrapped up the victory with a strike three minutes from time.
The defeat was the first of the season for the Canaries who are chasing a first French title since 2001.
Defending champions Paris Saint-Germain can break a three-way tie at the top of the table, alongside Reims and Rennes, if they can pick up at least a point at Monaco in the weekend's final match.
On Saturday, Lyon returned to winning ways as they rode a Nabil Fekir hat-trick to a 4-0 thrashing away to Caen while Rennes claimed their place in the top three with a 3-1 home victory over Toulouse.
Reims are the surprise table-toppers on goal difference following a 4-1 dismantling of suffering Brittany side Lorient and Lille won for the first time under new coach Herve Renard when they edged Ajaccio 1-0.
On Friday, Marseille came back to earth with a thud following their 6-0 thrashing of Troyes last week which was new coach Michel's first match in charge, but it all went wrong at Guingamp where they slumped to a 2-0 reverse.